Method of making a needle and a needle

ABSTRACT

A method is provided for forming a feature on a needle. In particular, a hollow, metal cannula has a first end, a second end and a substantially constant outer diameter extending over at least a portion of its length. An annular metal sleeve is provided that has a proximal shoulder and a distal shoulder. The length of the annular sleeve is less than the length of the constant diameter portion of the cannula. The sleeve has an inner diameter approximately equal to or less than the outer diameter of the constant diameter portion of the cannula. Two edges extend axially along the length of the sleeve, from the proximal shoulder to the distal shoulder, thereby defining a slit. The sleeve is positioned on the cannula at the constant outer diameter portion in an interference fit. An additional mechanical junction may be provided to secure the sleeve to the cannula. For example, the sleeve may be welded to the cannula using a laser welder at at least one edge of the sleeve near one of either the proximal face or the distal face. Alternatively and additionally, the sleeve may be crimped or glued to the cannula. In accord with another aspect of this invention, a needle is provided made in accord with this method.

FIELD OF THE INVENTION

The subject invention relates to the field of infusion therapy. Inparticular, the invention is related to an introducer needle having ashoulder disposed at a predetermined distance from the tip of the needleand to a method for making such a needle.

BACKGROUND OF THE INVENTION

Catheters, particularly intravenous (IV) catheters, are used forinfusing fluid, such as normal saline solution, various medicaments andtotal parenteral nutrition, into a patient or withdrawing blood from apatient. Peripheral IV catheters tend to be relatively short, and are onthe order of about one and one-half inches in length. The most commontype of IV catheter is an over-the-needle peripheral IV catheter. As itsname implies, an over-the-needle catheter is mounted over an introducerneedle having a sharp distal tip. The catheter and the introducer needleare assembled so that the distal tip of the introducer needle extendsbeyond the distal tip of the catheter with the bevel of the needlefacing up away from the patient's skin.

The catheter and introducer needle assembly is inserted at a shallowangle through the patient's skin into a peripheral blood vessel, i.e., asmaller blood vessel that is not connected directly to the heart but isone of the branches of the central blood vessels that is directlyconnected to the heart. In order to verify proper placement of theassembly in the blood vessel, the clinician confirms that there isflashback of blood in the needle and in a flashback chamber located atthe proximal end of the needle, which is typically formed as part of theneedle hub. Once proper placement is confirmed, the clinician appliespressure to the blood vessel by pressing down on the patient's skin overthe distal tip of the introducer needle and the catheter. This fingerpressure occludes further blood flow through the introducer needle. Theclinician withdraws the introducer needle, leaving the catheter inplace, and attaches a fluid-handling device to the catheter hub. Oncethe introducer needle is withdrawn from the catheter, it is a “bloodcontaminated sharp” and must be properly handled.

In recent years, there has been great concern over the contamination ofclinicians with a patient's blood and a recognition that “bloodcontaminated sharps” must be immediately disposed. This concern hasarisen because of the advent of currently incurable and fatal diseases,such as Acquired Immunosuppressive Deficiency Syndrome (“AIDS”), whichcan be transmitted by the exchange of body fluids from an infectedperson to another person. Thus, contact with the body fluid of anHIV-infected person should be avoided. As noted above, if an introducerneedle has been used to place a catheter in the vein of an HIV-infectedperson, the introducer needle may be a vehicle for the transmission ofthe disease. Although clinicians are aware of the need to properlyhandle “blood contaminated sharps,” in certain medical environments,such as emergency situations or as a result of inattention or neglect,needle sticks from contaminated introducer needles may occur.

As a result of the problem of accidental needle sticks by “bloodcontaminated sharps,” various needle shields have been developed.Examples of such shields are disclosed in U.S. Pat. No. 6,004,294 andU.S. patent application Ser. No. 09/717,148 (filed Nov. 21, 2000), bothincorporated herein by reference. These shields operate by engaging afeature, such as an enlarged diameter portion, formed on the needle. Theengaging means may take many forms, such as a spring gate biased tocontact the enlarged diameter portion of the needle when the tip of theneedle is within the shield. Due to the small size of the needle and itsdelicate structure, it has been difficult to provide a feature that canwithstand adequate force without affecting the operation of the needleitself. Further, such features have traditionally included a ramp, aradius or angled surface extending from the surface of the needle thatmay create difficulty in capturing the tip within the shield or mayresult in exertion of force on the needle in a non-axial direction.

SUMMARY OF THE INVENTION

It is therefore an advantage of one aspect of the instant invention toprovide a needle and method of making a needle that may be employed withvarious safety-engineered shielding devices.

It is an advantage of another aspect of the invention to provide aneedle and a method for making a needle having a feature with aright-angled shoulder.

It is an advantage of another aspect of the instant invention to providea needle having a sleeve secured to a cannula at a predeterminedlocation and a method for securing the sleeve to the cannula at thepredetermined location.

It is an advantage of yet another aspect of the instant invention toprovide a technique for securing a feature on a needle having a sharp,right angled shoulder that can be readily captured by an engaging meansin a needle shield and, once captured, can direct the forces from theengaging means to the needle in a substantially axial direction.

In accord with one aspect of the invention, a method is provided forforming a feature on a needle. In particular, a hollow, metal cannulahas a first end, a second end and a substantially constant outerdiameter extending over at least a portion of its length. An annularmetal sleeve is provided that has a proximal shoulder and a distalshoulder. The length of the annular sleeve is less than the length ofthe constant diameter portion of the cannula. The sleeve has an innerdiameter approximately equal to or less than the outer diameter of theconstant diameter portion of the cannula. Two edges extend axially alongthe length of the sleeve, from the proximal shoulder to the distalshoulder, thereby defining a slit. The sleeve is positioned on thecannula at the constant outer diameter portion in an interference fit.An additional mechanical junction may be provided to secure the sleeveto the cannula. For example, the sleeve may be welded to the cannulausing a laser welder at at least one edge of the sleeve near one ofeither the proximal face or the distal face. Alternatively andadditionally, the sleeve may be crimped or glued to the cannula. Inaccord with another aspect of this invention, a needle is provided thathas been made in accord with this method.

Certain implementations of this aspect of the invention provide that theproximal shoulder is perpendicular to the axis of the cannula or thedistal shoulder is perpendicular to the axis of the cannula. The sleevemay be welded to the cannula proximate to both the proximal face and thedistal face, or a seam weld may be applied along the length of thesleeve. Alternatively or additionally, the sleeve may be crimped orglued to the cannula. The sleeve may be formed by rolling a flat metalsheet into an annular shape, such as a cylinder, and then slipped ontothe cannula. A window may be formed in the sleeve at a predeterminedposition with respect to the slit and the sleeve may be welded to thecannula at the window. Such a window may be disposed in the sleeve at aposition 180 degrees from the slit.

In accord with another aspect of the invention, a distinct mechanicaljunction is formed between the sleeve and the cannula to secure thefeature in place. For example, a notch is formed in the outer surface ofthe cannula at a predetermined position along the length of the cannula.A cylindrical sleeve has an inner cavity with an inner diameter that isless than the outer diameter of the outer surface of the cannula. Thesleeve is positioned over the cannula such that the notch is disposedwithin the inner cavity. The sleeve is crimped such that at least aportion of the sleeve is deformed radially inward, causing the sleeve toengage the notch. Certain implementations of this aspect of theinvention provide that the sleeve is welded to the cannula aftercrimping or that an adhesive is employed to join the sleeve to thecannula. The use of an adhesive may be particularly advantageous to holdthe sleeve in place before the crimp or weld is formed.

In accord with yet another aspect of the invention, a needle includes ahollow, metal cannula having a first end, a second end, a beveled tip atthe second end, an axis, a cannula length extending from the first endto the second end, and an outer diameter. A distinct annular metalsleeve is fixedly attached to the cannula at a predetermined positionwith respect to the tip. The sleeve has a proximal shoulder and a distalshoulder, and a sleeve length extending from the proximal shoulder tothe distal shoulder. At least one of the proximal shoulder or the distalshoulder is perpendicular to the axis of the cannula. Certainimplementations of this aspect of the invention provide that the sleevehas two edges extending axially along the sleeve length from theproximal shoulder to the distal shoulder, thereby defining a slit and aweld is disposed along the slit. A flash opening may be positioned inthe cannula, proximal to the sleeve, that would provide the caregiverwith a visual indication when the beveled tip of the needle has accessedthe patient's vein. Radially extending tabs may be positioned on thesleeve to orient the needle during manufacture and use

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a cannula and sleeve in accordwith one aspect of the invention.

FIG. 2 is a perspective view of a cannula and sleeve in accord with anaspect of the invention with a seam weld.

FIG. 3 is an exploded perspective view of a cannula and anover-the-needle catheter in accord with an aspect of the invention.

FIG. 4 is a cut-away side view of the cannula and catheter of FIG. 3.

FIG. 5 is a perspective view of a cannula and a sleeve in accord withanother aspect of the invention.

FIG. 6 is a side elevation view of the cannula and sleeve of FIG. 5.

FIG. 7 is a top elevation view of a cannula and sleeve in accord withanother aspect of the invention.

FIG. 8 is a bottom elevation view of the cannula and sleeve of FIG. 7.

FIG. 9 is a perspective view of a sleeve in isolation.

FIG. 10 is a front elevation view of the sleeve of FIG. 9.

FIG. 11 is a side elevation view of the sleeve of FIG. 9.

FIG. 12 is a top elevation view of a sheet used to form the sleeve ofFIG. 9.

FIG. 13 is a top elevation view of a cannula and sleeve in accord withan aspect of the invention.

FIG. 14 is a side elevation view of the cannula and sleeve of FIG. 13.

FIG. 15 is a cut-away side view of the cannula and sleeve of FIG. 13.

FIG. 16 is a perspective view of a sleeve for use in accord with aspectsof the invention.

DETAILED DESCRIPTION

As used herein, the term “proximal” refers to a location on the needle 1that, during normal use, is closest to the clinician using the deviceand farthest from the patient in connection with whom the device is used(the right side of FIG. 4). Conversely, the term “distal” refers to alocation on the needle that, during normal use, is farthest from theclinician using the device and closest to the patient in connection withwhom the device is used (the left side in FIG. 4).

In various stages of the manufacture of needle assemblies and during theuse of needles, it would be advantageous to have a distinct feature onthe needle 1 that is secured at a fixed location and orientation withrespect to the rest of the needle 1, particularly the tip 14. Forexample, such a feature may be employed to orient the needle 1 withrespect to a needle hub or holder. Consequently, the needle tip 14 wouldalso be at a fixed orientation with respect to the holder. A caregiverwould thus know immediately to orientation of the needle tip 14 bysimply grasping the holder. Further, such a feature may be more readilygraspable by machines designed to automatically manufacture needles andover-the-needle catheter assemblies. The feature may be used to engage aledge 101 in a catheter 100 (see FIG. 4), thereby positioning the needleat a particular location within the catheter and ensuring that the tip14 of the needle extends out of the catheter a satisfactory distance.Additionally, such a feature may be more readily grasped by a safetydevice designed to capture the needle tip 14 after use.

In accord with an aspect of the invention, a needle 1 includes a cannula10 having a ferrule or sleeve 40 attached at a fixed, predeterminedposition along the length of the cannula. As will be discussed morefully below, the sleeve 40 is preferably sized with an inner diameterthat is smaller than the outer diameter of the cannula. Consequently,there is an interference fit between the sleeve 40 and the cannula whichhelps maintain the sleeve in its predetermined position. Additionalmechanical junctions or bonds 60 may be provided to better maintain thesleeve 40 in place. With the sleeve 40 in place, the needle 1 includes afeature (which may include the proximal shoulder 44 and/or distalshoulder 45 of the sleeve, or the sleeve itself, or some other structureattached to or formed integral with the sleeve, such as a tab 80) thatcan be employed for various purposes related to the manufacture and useof the needle 1. For example, once formed, the needle 1 may be insertedinto a catheter 100 for insertion into the tissue of a patient. Afteruse, the needle 1 may be withdrawn from the catheter. The needle tip 14may then be captured within a safety-engineered shielding device thatgrips the feature such as disclosed in U.S. Pat. No. 6,004,294 and U.S.patent application Ser. No. 09/717,148, incorporated herein byreference.

The cannula 10 includes a proximal end 11 and a distal end 12 extendingalong an axis 13. Typically, the cannula has a cylindrical shape.Preferably, at least a portion 21 of the cannula has a constant outerdiameter. A beveled tip 14 is positioned at the distal end of thecannula. The beveled tip may be formed of two beveled surfaces, aproximal bevel 15 and a distal bevel 16 (see FIG. 2), that are disposedat different angles from the axis of the cannula to ease entry into apatient's vein. The cannula includes an outer surface 20 and an innersurface 19. The inner surface 19 defines a central cavity 17 thatextends from the proximal end of the cannula to the distal end, forminga tip opening 23 at the distal end.

A flash opening 18 is located in the wall of the cannula 10, creating afluid flow path from the central cavity 17 to the exterior of thecannula within the catheter 100. Preferably, the flash opening isproximal to the sleeve 40. The catheter is operably engaged to a flashchamber 90. The flash chamber may simply be the annular space about theneedle within the catheter (see FIG. 4) or a separate chamber located ina needle hub. During use, this flow path provides the caregiver with avisual indication that the vein has been successfully entered because asmall amount of blood will flow through the tip opening, through theflash opening and into the flash chamber where it is visible to thecaregiver. As shown in FIG. 4, the catheter is translucent so that bloodin the annular space 90 is visible to the caregiver.

The ferrule or sleeve 40 preferably has a substantially cylindricalshape (see FIG. 9) formed by an exterior surface 42, an interior surface43, and a length 47 extending from a distal face 145 to a proximal face144. The interior surface 43 defines an inner cavity 51. Importantly, inaccord with certain implementations of the invention, the sleeve 40 issized to tightly fit on the cannula in an interference fit. The length47 of the sleeve 40 is preferably no longer than the length of theconstant diameter portion 21 of the cannula. As can be seen in FIG. 4,when the sleeve 40 is positioned on the cannula, the distal face forms adistal shoulder 45 and the proximal face forms a proximal shoulder 44.Preferably, the distal shoulder and the proximal shoulder areperpendicular to the outer surface 20 of the cannula 10 and to thecannula axis 13.

A slit 50 is formed in the sleeve 40 and defined by two edges 41.Preferably, the slit extends axially through the sleeve 40 from theproximal face 144 to the distal face 145. The slit may also have othershapes and still practice the invention. In particular, the slit mayproceed around the sleeve 40 in a spiral shape or other curved shapes.Before positioning the sleeve 40 on the cannula, the edges are adjacentor nearly adjacent (see FIG. 5). As the sleeve 40 is forced onto thecannula, the edges separate to accommodate the larger outer diameter ofthe cannula within the inner cavity 51.

The sleeve 40 may be formed in any manner such as extruding, casting orthe like. If the sleeve 40 is initially formed as a complete cylinder,the slit 50 can be formed in the sleeve, such as by cutting, burning andso on. In one implementation of the invention, the sleeve 40 is formedof a flat sheet 46 (see FIG. 12). The sheet is rolled into a nearlycylindrical shape, bringing the edges together and thereby forming theslit. The sheet is sized so that the slit extends over less than 180degrees of arc along the diameter of the sleeve when the sleeve ispositioned on the cannula. Preferably, the slit extends over 20 degreesof arc or less when the sleeve is positioned on the cannula. It will beappreciated that the slit may be larger or smaller and still practicethe invention. Further, in certain implementations, the slit may beformed as a groove disposed in the sleeve 40 that does not extend fullythrough the sleeve 40 radially (that is, the edges are connected by athin webbing before mounting the sleeve on the cannula).

Once the sleeve 40 is formed, it is slipped over the distal end 12 ofthe cannula 10 and positioned at a predetermined location on a constantdiameter portion 21 of the cannula. Preferably, the sleeve 40 is locateda distance from the tip 14 such that the tip and the sleeve may besecured within a shield after use, as discussed in U.S. Pat. No.6,004,294, incorporated herein by reference, and U.S. application Ser.No. 09/717,148, incorporated herein by reference. It will be appreciatedthat the sleeve 40 may be located at other locations and still practiceaspects of the invention. Further, the sleeve 40 may be formed in othermanners and be positioned on the cannula in different ways and stillpractice aspects of the invention. For example, the flat sheet 46 may berolled directly onto the cannula and secured in place as disclosedherein.

As discussed above, the diameter of the inner cavity 51 of the sleeve 40is preferably less than the diameter of the outer surface 20 of thecannula 10, creating a close interference fit between the sleeve and thecannula. The edges 41 of the sleeve 40 are forced apart to accommodatethe outer diameter of the cannula. If webbing connects the edges, it isbroken as the cannula is forced into the inner cavity. In any event,there is preferably direct contact between the interior surface 43 ofthe sleeve 40 and the outer surface 20 of the cannula when the sleeve ispositioned on the cannula.

The interference fit between the interior surface 43 of the sleeve 40and the outer surface 20 of the cannula prevents movement of the sleeve40 along the length of the cannula under certain loads. Indeed, theinterference fit alone may provide adequate resistance to the movementof the sleeve 40 for a particular application such that the interferencefit may be deemed an adequate mechanical junction. In certaincircumstances, however, a greater resistive force will be desired. Inthose circumstances, an additional mechanical junction 60 is provided,securing the sleeve 40 to the cannula. For example, the sleeve 40 may bewelded to the cannula using a laser welder. As depicted in FIG. 2, alaser beam 301 from a laser welding device 300, such as an Nd: Yag laserwelder, model Luxstar LX50 may be directed at contact points on thesleeve 40. The sleeve and the cannula are in direct physical engagementat the contact points. A seam weld 160 may then be created along theslit 60 by delivering a laser beam in a series of spots over the lengthof the sleeve.

Other techniques for welding may also be employed. Referring to FIGS. 7and 8, two of the contact points or weld points 61 are positioned alongthe edges 41 at the slit 50, one near the proximal shoulder 44 and onenear the distal shoulder 45. The laser beam is directed at the junctureof the edge and the cannula at the slit. The laser melts the material ofthe sleeve 40 and the cannula, which, in turn, cools to form a weld,integral with both the sleeve 40 and the cannula, securing themtogether. Two other contact points or weld points 64 are disposed on theopposite side of the sleeve 40, 180 degrees from the slit. Again, theseweld points are disposed near the proximal shoulder 44 and the distalshoulder 45. The laser beam is directed at the exterior surface 42 ofthe sleeve 40, melting through the wall of the sleeve so that the beamsmelt at least some portion of the outer surface 20 of the cannula 10.The melted portions of the sleeve 40 and the cannula 10 cool to form aweld, integral with both the sleeve and the cannula, securing themtogether.

These four welds may be created by splitting a single laser beam intofour beams, and applying them to the desired weld points for acontrolled period of time, depending on the dimension of and materialsforming the sleeve 40 and the cannula 10, as well as the desiredresistive force to be withstood by the mechanical junction 60. It willbe appreciated that other techniques for welding, in particular othertechniques for laser welding, may be employed and still practice aspectsof the invention. For example, the weld may be provided at locationsdistinct from the slit. Currently, on one preferred application of theinvention, two seam welds 160 are formed disposed 180° from each other,neither being located along the slit. The laser beam is delivered to thesurface of the sleeve and creates a weld, bonding the sleeve to thecannula along both seams. Alternatively or additionally, a window 48 maybe provided in the sleeve. The mechanical junction 60 can be formed by aspot weld at the edge of the window (see FIGS. 3 and 4).

The dimensions and materials of the sleeve 40 and cannula 10, as well asthe operation of the laser welder, will depend on the particularapplication for the needle 1. It is preferred that the sleeve 40 and thecannula be formed of a similar alloy to ensure that a satisfactorymechanical bond is formed by the laser weld or other mechanicaljunction. In one application of the instant invention, the cannula ismade of fully hard 301 (or 302) stainless steel and has an outerdiameter of between 0.007 and 0.080 inch (including, around 0.055 inch).The sleeve 40 is formed from a sheet of fully hard 301 (or 302)stainless steel about 0.002 inch thick and about 0.050 inch long. Theweld points are preferably about 0.005 inch inward from the proximal anddistal shoulders. Most preferably, the sleeve 40 contacts the cannulawhere the weld is applied. In any event, it is preferred that there be agap of no more than 0.0010 inches at a desired weld point. The laserbeam is applied to the weld points for a period of 0.2 seconds at 100 Hzat a setting of 30-50 KW. The resulting weld at the weld point is about0.010 inch in diameter and can withstand an axial force of about 30-50lbs.

Referring to FIGS. 13-15, another form of mechanical junction may beemployed in connection with an aspect of the instant invention. Crimpnotches 70 are formed in the cannula at a desired location, such as atthe otherwise constant diameter portion 21 of the cannula (constant,that is, excluding the crimp notches). Preferably, the crimp notches donot penetrate the wall of the cannula. However, the crimp notches 70 maybe formed as cut outs in the cannula wall. Further, the flash notch 18may be employed as a crimp notch. The number, location and shape of thecrimp notches 70 may be selected based on the particular application ofthe needle. For example, two crimp notches may be employed, disposed onopposite sides of the cannula at a position distal to the flash notch 18(see FIG. 15). The sleeve 40 is formed and slipped over the cannulauntil it is disposed directly over the crimp notches, capturing thecrimp notches within the inner cavity 51. The sleeve 40 is then crimpedinto the crimp notches 21, creating a mechanical engagement at junction63 between the sleeve and the cannula. The sleeve 40 may also be securedto the cannula using an adhesive material 62 or weld points 61. The useof an adhesive material may be particularly advantageous to maintain thesleeve in position on the cannula until crimping or welding iscompleted.

As discussed above, the feature on the needle 1, such as the sleeve 40and/or its proximal and distal shoulders, are preferably symmetric aboutthe axis of the catheter. It will be appreciated that the sleeve 40 mayhave other distinct shapes and still practice the invention. Forexample, tabs or ribs 80 (see FIG. 16) may be formed on the sleeve 40that extend radially outward or which extend axially from the distalshoulder or the proximal shoulder along the surface of the cannula. Suchtabs or ribs may be employed to orient the cannula (and thus the needletip 14) with the catheter 100 (and thus a hub that is grasped by acaregiver). Further, such tabs or ribs may be used as a register toobserve and control the orientation of the cannula during themanufacturing process. The tabs or ribs may also be designed tocooperate with various structures in a needle shield to better capturethe needle tip 14.

Further, as disclosed herein, the cannula has a substantiallycylindrical shape. It will be appreciated that the cannula may haveother shapes and still practice aspects of the invention. For example,the cannula may have an oval cross section such that the sleeve 40contacts the cannula only along the major axis of the oval. Conversely,the sleeve may be formed with an inner cavity having an oval crosssection such that it contacts the outer surface 20 of the cannula at theminor axis of the oval. The mechanical junction may then be formed atthose contact points, such as by welding, using an adhesive material 62or crimping the sleeve 40 into a notch on the cannula.

It is preferred that the sleeve 40 actually contacts the cannula at theweld point during welding. Such a contact is preferably achieved by theinterference fit between the sleeve 40 and the cannula. However, it willbe appreciated that the sleeve 40 may be sized such that there is nointerference fit and practice aspects of the invention. For example, asolder material may be disposed about the cannula as the sleeve 40 isslipped into position before welding. Advantageously, a solder that alsofunctions as an adhesive material may be employed. If the internaldiameter of the sleeve 40 is larger than the outer diameter of thecannula, there will be a space between the cannula and the sleeve thatmight interfere with satisfactory laser welding. To overcome thisdifficulty in this situation, the sleeve 40 may be biased in a directionagainst the outer surface 20 of the cannula to achieve a contact pointwhere welding can take place. Further, other welding techniques may notrequire the close positioning of the sleeve 40 and the cannula toachieve a satisfactory weld. In fact, in certain circumstances, thesleeve 40 may be sufficiently thick that enough material can be meltedby the laser welder to effect an adequate weld without affecting theintegrity of the sleeve.

As discussed herein, four spot weld points or two seam welds areemployed. Any number of welds and weld points may be employed as isrequired to achieve a satisfactory bond between the sleeve and thecannula for a given application. Further, the weld points and seams maybe located at other positions and still practice aspects of theinvention. For example, the sleeve 40 may be secured to the cannula witha single weld formed in the sleeve at any position, such as a positionremote from the slit. The weld point may be at the juncture of theproximal shoulder and/or the distal shoulder and the outer surface 20 ofthe cannula. The weld may be a single contiguous line extending axiallyalong the full length of the sleeve 40, or circumferentially about adiameter of the sleeve.

The sleeve 40 is preferably positioned along the cannula at a pointdistal of the flash notch 18. It will be appreciated that the sleeve maybe positioned at other locations and still practice aspects of theinvention. For example, the flash notch 18 may be positioned between thesleeve 40 and the tip of the cannula. Alternatively, the sleeve 40 maybe positioned in engagement with or partially covering the flash notch18. Further, the slit may be orientated at different locations withrespect to the flash notch 18 and practice aspects of the invention.

The proximal shoulder and the distal shoulder preferably formright-angled surfaces with the outer surface 20 of the cannula. It willbe appreciated that the shoulders may have different shapes and stillpractice aspects of the invention. For example, the shoulder may beprovided with an undercut at the cannula surface, creating a crevicethat may engage certain types of grasping mechanisms contained withinshields Further, the proximal face 144 and distal face 145 may havecurved or notched surfaces, depending on the particular application ofthe invention.

Although the invention is described herein in connection with a needle 1employed with a peripheral IV catheter and a safety shield, it isunderstood that the invention is applicable to other needles, such ashypodermic needles, epidural needles and so forth. In addition, whilethis invention is satisfied by embodiments in many different forms,preferred embodiments of the invention are shown in the drawings anddescribed in detail herein. The scope of the invention is measured bythe appended claims.

1. A method of forming a feature on a cannula comprising: providing ahollow, metal cannula having a first end, a second end, an axis, alength extending from the first end to the second end, and an outersurface extending over at least a first portion of the length; providingan annular metal sleeve with an exterior surface, a proximal shoulderand a distal shoulder, the sleeve having a length extending from theproximal shoulder to the distal shoulder, wherein the length of thesleeve is less than the length of the first portion of the cannula;wherein the sleeve includes two edges extending axially along the lengthof the sleeve, from the proximal shoulder to the distal shoulder,thereby defining a slit; positioning the sleeve on the cannula at thefirst portion of the cannula such that the sleeve contacts the cannulaat least one contact point; and welding the sleeve, using a laserwelder, to the cannula at the contact point to form a mechanicaljunction.
 2. The method of claim 1 wherein the mechanical junction is aseam weld extending the length of the sleeve.
 3. The method of claim 1wherein the distal shoulder is perpendicular to the axis of the cannula.4. The method of claim 3 wherein the proximal shoulder is perpendicularto the axis of the cannula.
 5. The method of claim 1 wherein the contactpoint is disposed along the slit.
 6. The method of claim 5 wherein thecontact point comprises at least two contact points that are is disposednear to both the proximal shoulder and the distal shoulder.
 7. Themethod of claim 1 wherein welding comprises delivering a laser beam tothe exterior surface of the sleeve and welding through the sleeve to thecannula.
 8. The method of claim 7 wherein a rib is mounted to thesleeve, extending, at least in part, radially outward from the exteriorsurface of the sleeve.
 9. The method of claim 1 wherein the slit extendsover less than 20 degrees of arc of the sleeve when it is positioned onthe cannula.
 10. The method of claim 1 further comprising providing aflat metal sheet and rolling the sheet into an annular shape to form thesleeve.
 11. The method of claim 1 further comprising forming a window inthe sleeve at a predetermined position with respect to the slit andwelding the sleeve to the cannula at the window.
 12. The method of claim11 wherein the window is disposed in the sleeve at 180 degrees from theslit.
 13. The method of claim 1 further comprising positioning anadhesive material between the sleeve and the cannula, securing thesleeve to the cannula.
 14. The method of claim 1 wherein: the distalshoulder is perpendicular to the axis of the cannula; at least a firstweld is disposed at a first location on the sleeve; and at least asecond weld is disposed on the sleeve at a second location, wherein thesecond location is disposed between 170 degrees and 190 degrees of arcabout the cannula axis from the first location.
 15. A method of forminga feature on a cannula comprising: providing a cannula having a firstend, a second end, an axis, a length extending from the first end to thesecond end, and an outer diameter extending over at least a firstportion of the length; providing a sleeve with a proximal shoulder, adistal shoulder, an inner diameter, a sleeve length extending from theproximal shoulder to the distal shoulder, and edges extending from theproximal shoulder to the distal shoulder, thereby forming a slit;wherein the sleeve has an inner diameter less than the outer diameter ofthe first portion of the cannula; positioning the sleeve on the cannulaat the first portion of the cannula in an interference fit such that theslit expands to accommodate the cannula; and joining the sleeve to thecannula with a mechanical junction.
 16. The method of claim 15 whereinthe mechanical junction is a weld.
 17. The method of claim 15 whereinthe sleeve is crimped to the cannula.
 18. The method of claim 15 whereinthe mechanical junction is a seam weld formed by a laser welderextending substantially the full length of the sleeve.
 19. The method ofclaim 15 wherein the sleeve is glued to the cannula by an adhesivematerial.
 20. The method of claim 19 further comprising crimping thesleeve to the cannula.
 21. The method of claim 19 wherein the sleeve iswelded to the cannula.
 22. A cannula formed by the method set forth inclaim 15.